tidal-cv

TidalCycles continuous control voltage utilities

Setup

First evaluate this line in the supercollider environment to install tidal-cv:

Quarks.install("https://github.com/colevscode/tidal-cv.git");

Then add this line to your supercollider startup.scd file after loading superdirt.

~tidalcv = TidalCV(~dirt, -1, 9, 0.05, 0.025);

TidalCV is initialized with the dirt instance ~dirt followed by values for minOct, maxOct, triggerHold and latencyCorrection. See the section on the TidalCV class for more information.

You may need to adjust the above parameters. You can do so by following the calibration procedure below.

Optional: adjust supercollider's latency. The default is 0.02. I bump it to 0.05 to give the server a little more time to process events, and ensure the cv synths can correctly output the signal. Example: s.latency = 0.05.

Usage

Once you've initialized tidal-cv, you will have access to several new synths in the tidalcycles environment.

Note: generally the synths defined by tidal-cv send DC signals with values between -1 and 1. What your audio adapter does with this depends on how it's configured. I'm using an ES-9 which multiplies the signal by 10, generating -10v to +10v.

The following cv and gate synths are exported to tidal by tidal-cv:

cv0 - cvN: Control voltage synths for each of N orbits. Each cv will target channel N * numChannels, for example, if you're using 2 channels, cv0 = channel 0, cv2 = channel 4.
cv0_pitch - cvN_pitch: Alternate way to control the same cv synths above, however notes are interpreted as frequencies (such as "a5 or bs3") and mapped to voltages using a 1v/octave scale. The frequency is converted from exponential to linear, using "a5" (freq 440) as the origin. Then it's scaled to an octave range defined by minOct and maxOct. The formula for converting frequencies is (log2(freq/440)-minOct)/(maxOct-minOct). My oscillator is happy with a range of -1 to 9 octaves, but you'll have to experimentally determine what range works for your oscillator.
cv0_slew - cvN_slew: Synths that controls the slew (or portamento) value of the relevant cv.
gate0 - gateN: Synths that output a voltage intended to be used as a gate. Each gate will target channel N * numChannels + 1, for example, if you're using 2 channels, gate0 = channel 1, gate2 = channel 5. By default these expect notes in the range -1 to 1 which should generate -10v to +10v from your audio adapter.
gate0_trig - gateN_trig: Synths that trigger a +10v pulse for a short hold period defined by triggerHold.
gate0_slew - gateN_slew: Slew control for the gate synths.

For an example use of these synths within tidal, see tidal-example.hs.

Usage Example

Here's a short example of how to use tidal-cv in tidalcycles.

-- turn on cv1 and gate1
once $ stack [s "cv1_on", s "gate1_on"]

-- simple baseline
d1 $ stack [
  n "a3 b3 bs3 a4 " # s "cv1_pitch", 
  n "1!4" # s "gate1_trig"
]

For a more indepth example see tidal-example.hs.

The TidalCV class

This quark creates a single TidalCV class with a constructor that initializes and exports a set of synths to tidalcycles. (See the section on usage above)

The following variables are passed to the TidalCV constructor, and can later be accessed via the returned instance.

minOct: A value that represents the minimum frequency in octaves below middle A. Used to calibrate 1v/octave.
maxOct: A value that represents max frequency in octaves above middle A.
triggerHold: Time in seconds to hold the gate high during a gate trigger event.
latencyCorrection: An adjustment to the delay time when sending cv messages. Units are seconds. See calibration procedure below.

For example, to initialize a TidalCV instance, add the following line to your supercollider startup.scd file:

~tidalcv = TidalCV(~dirt, minOct: -1, maxOct: 9, triggerHold: 0.05, latencyCorrection: -0.025);

Later you can adjust the above variables using the tidal-cv instance:

~tidalcv.latencyCorrection = 0.0

Calibration

Calibrating the CV pitch synths

It may be necessary to calibrate the 1v/oct range generated by the cv pitch synths (eg, cv1_pitch).

To do this, patch an oscillator module into one of your audio adapter's CV outs. Then generate a sequence of pitches from tidal from both a CV synth, and an audible synth:

d1 $ stack [
  n "a3 a5 a7 a9" # s "cv1_pitch",
  n "1" # s "gate1"
]

d2 $ n "a3 a5 a7 a9" # s "arpy" # channel 0

This will generate a sequence of 1v/oct levels from channel 2 and a constant high gate from channel 3. You'll also hear the sequence of tones from tidal on channel 0.

By listening to these simultaneously you can fine-tune your modular synth osciallator's 1v/oct knob until the two sounds match up. If you find that your modular synth is playing an octave high or low, you can adjust the octave range using the ~tidalcv instance in supercollider:

~tidalcv.minOct = -2
~tidalcv.maxOct = 8

Once you've figured out a range that works, update your startup.scd file to use the new values when instantiating the TidalCV instance.

// your new values
~tidalcv = TidalCV(~dirt, -2, 8, 0.05, 0.025);

Calibrating `latencyCorrection`

It may be necessary to calibrate the delay time used to send messages to the cv synths. I suggest generating a cv clock output, use it to gate an oscillator on your modular synth, and simultaneously generate a simple beat pattern from tidal. Then, listening to the two tracks, adjust the latencyCorrection value until they're in sync. Alternately you can patch both to a scope and line them up visually.

Example:

d1 $ stack [
  n "1!4" # s "gate1_trig",
  s "hh!4" 
]

colevscode/tidal-cv